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Nafion coated glassy carbon electrodes (NCE) are employed for preconcentrating and detecting Fe2+ and Fe3+ cations from aqueous solutions. The influence of the supporting electrolyte composition and of the redox state on the analyte partitioning within the Nafion coating are examined. By using cyclic voltammetry, the ion‐exchange voltammetric determination of iron in the μM concentration range is achieved from voltammetric peak currents relevant to the reversible redox process: Fe3++e⇋Fe2+. Depending on the starting potential of the voltammetric scan, all the iron is initially converted to the Fe(III) or Fe(II) redox state, so that, from the voltammogram, the overall concentration of iron is always obtained. However, the simple measurement of the open circuit potential at the NCE before starting the scan allows one to get information on the ratio between Fe(III) and Fe(II) incorporated in the Nafion coating. From relevant ion‐exchange distribution coefficients, open circuit potential values can be related to the Fe(III)/Fe(II) concentration ratio in the sample. The use at the NCE of a new electroanalytical technique named multiple square‐wave voltammetry in the double differential mode allows the significative lowering of detection limits pushing the operative range of the method in the nM range. Application to analysis of Fe(II) in the pore‐waters of sediments of the lagoon of Venice (Italy) is presented.

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Powder coatings have been used for coating metal substrates in industrial applications. The incorporation of nanofillers as muscovite mica and montmorillonite (MMT) can improve the properties of the coatings. The objective of this study is to develop, apply and characterize a hybrid powder coating (30% epoxy/70% polyester) adding nanofillers in concentrations of 2, 4 and 6 phr separately in a twin screw extruder. The characterization of the coatings was performed by thermal, mechanical and chemical analysis. The incorporation of clay into the polymer increased the surface roughness resulting in a diffuse reflection of incident light and on a gloss reduction. The muscovite mica presented a lamellar structure, constituted by a set of overlapping parallel plates. The morphology analysis showed that the MMT presented irregular agglomerates resulting in inferior mechanical properties to coatings with muscovite mica. In the salt spray test, all samples showed high corrosion protection, around 850 hours.

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For the polyhedral oligomeric silsesquioxane (POSS) nanocomposites with epoxy resins, the POSS functionality is an important issue since these compounds will be diluted in the resin that will later undergo a chemical reticulation process. In this study, mono, tri and octa‐functional POSS containing glycidyl groups were dispersed in an epoxy resin by applying ultrasound. Based on the results obtained from the transmission electron microscopy, POSS tended to form an ordered phase to minimize the interfacial tension; however, this form was influenced by its functionality. The use of mono‐functional POSS shows finer dispersion and promotes an increase in the resin glass transition temperature. However, the octa‐functional POSS leads to improvement in thermal stability as seen in the degradation analysis. These results showed that the equilibrium of the dispersed nanoparticle is more evident for lower functionalized particles since higher functionalized ones hinder diffusion movements which ultimately form an ordered and dispersed phase in the resin during reticulation. POLYM. COMPOS., 38:E229–E236, 2017. © 2016 Society of Plastics Engineers